A known autostereoscopic display device is described in GB 2196166 A. This known device comprises a two dimensional liquid crystal display panel having a row and column array of display pixels acting as an image forming element to produce the display. An array of elongate lenticular elements extending parallel to one another overlies the display pixel array and acts as a view forming element. The display pixels are observed through these lenticular elements.
The lenticular elements are provided as a sheet of elements, each of which comprises an elongate semi-cylindrical lens element. The lenticular elements extend in the column direction of the display panel, with each lenticular element overlying a respective group of two or more adjacent columns of display pixels.
In an arrangement in which, for example, each lenticule is associated with two columns of display pixels, the display pixels in each column provide a vertical slice of a respective two dimensional sub-image. The lenticular sheet directs these two slices and corresponding slices from the display pixel columns associated with the other lenticules, to the left and right eyes of a user positioned in front of the sheet, so that the user observes a single stereoscopic image.
In other arrangements, each lenticule is associated with a group of three or more adjacent display pixels in the row direction. Corresponding columns of display pixels in each group are arranged appropriately to provide a vertical slice from a respective two dimensional sub-image. As a user's head is moved from left to right a series of successive, different, stereoscopic views are perceived creating, for example, a look-around impression.
Document US-B1-6710 920 discloses a multi-view autostereoscopic display device comprising an image forming means, a view forming means having an array of view forming elements, and a driving means.
The above described devices provide an effective three dimensional display. However, it will be appreciated that, in order to provide stereoscopic views, there is a necessary sacrifice in the horizontal resolution of the device. For example, a display panel having an array of 600 rows and 800 columns of display pixels may provide a four-view autostereoscopic display in which each view comprises an array of 600 rows and 200 columns of display pixels. This substantial difference between vertical and horizontal resolution is undesirable.
Furthermore, it will also be appreciated that there is a trade off between the viewing angle of the display and the perception of three dimensional depth in the display. In particular, to provide a display having a wide viewing angle, it is necessary to distribute the projected views over a large angle, for example 60°. However, such a display provides a shallow three dimensional image with little perception of depth. In contrast, in order to provide a realistic three dimensional image with good depth, it is necessary to concentrate all of the projected views across a small viewing angle. It can be shown that the depth range within which a three dimensional display is perceived without excessive blurring is approximately proportional to n/tan(θ/2), where n is the number of views and θ is the viewing angle of the display.